Heat Exchange System and Method

ABSTRACT

A dual fluid heat exchange system is presented that provides a stable output temperature for a heated fluid while minimizing the output temperature of a cooled fluid. The heated and cooled fluids are brought into thermal contact with each other within a tank. The output temperature of the warmed fluid is maintained at a stable temperature by a re-circulation loop that connects directly to the mid portion of the tank such that the re-circulated fluid flow primarily warms only a re-circulation section of the tank. The other, lower flow rate, section of the tank may be positioned so that it has a cooler temperature and thus serves to increase the efficiency of the heat exchange by extracting extra heat energy out of the cooled fluid before it leaves the tank. Alternatively, the low flow rate section of the tank may be warmer than the re-circulated section, and thus allow the re-circulated section to be cooler than the output temperature of the warmed fluid.

FIELD OF THE INVENTION

The present invention relates to heat exchange systems, and moreparticularly to a heat exchange system and method by which a first fluidis efficiently warmed to a consistent temperature by a second fluid.

BACKGROUND OF THE INVENTION

Heat exchange systems have been used for different purposes, such aswarming water used for domestic, commercial, or industrial purposes.Designers of heat exchange systems have faced many challenges such aslimitations on the size of the heat exchanger. Additionally, there is aneed for the warmed fluid to exit the system at a consistenttemperature. Managing the temperature of the cooled fluid leaving thesystem is also a challenge facing heat exchange systems due toefficiency and regulatory concerns.

Changes in the demand for heating require that heat exchange systems beable to provide vastly different amounts of heating, which can lead tosubstantial temperature changes in the output of the warmed fluid.Conventional methods of stabilizing the output temperature of the warmedfluid often rely on adjusting the flow rate of the fluid to be cooled.Although this approach may reduce the variability of the warmed fluidoutput temperature, the cooled fluid temperature leaving the heatexchanger can vary drastically.

Conventional systems used to heat water often have two fluid circuits.Typically water to be heated circulates in the first fluid circuit in aliquid state while steam circulates in the second fluid circuit attemperatures that are often above the boiling point of water. Bothcircuits meet at a heat exchanger unit where the cool water is warmed byflowing over thermally conductive conduits containing the hightemperature steam. The water exits the heat exchanger in a heated state,and if the demand for hot water increases, the flow rate of the hotwater vapor is simply increased.

In conventional systems, the temperature of the heated water at theoutlet varies based on the outgoing water flow rate variations and/oraccording to incoming water temperature variations. As a result of thevariable flow rate through the heat exchanger, the quantity of energytransmitted cannot be precisely controlled causing the temperature ofthe output water to vary. Additionally, the high temperature of thesteam limits control, but is needed for high usage situations. In lowusage situations, the steam will often warm the water up to atemperature beyond that which is desired.

A varying output temperature of the cooled fluid from the heat exchangercan reduce the efficiency of the energy exchange since energy remainingin the cooled fluid is often wasted. There are also many instances wherethere are requirements and regulations on the temperature of the cooledfluid leaving the heat exchanger. In systems where the cooled fluid isnot returned to its source for reheating, the cooled fluid is oftendumped into a sewer system or waterway. In addition to beinginefficient, dumped fluids often must be below a specified temperatureto avoid damaging sewer systems or to avoid causing thermal pollutionthat can lead to problems such as algae blooms.

In addition to the other problems associated with heat exchangers, floorspace is often at a premium in modern mechanical rooms so it isdesirable to have a heat exchanger with a minimal footprint. The costdifference in using a system with a small 1.75 square yard footprintversus having to stack multiple regular horizontal exchangers can bethousands of dollars. Thus, it is desirable to provide a verticallyoriented heated exchanger with a minimal footprint. Additionally,retrofit applications require heat exchangers to be placed in smallareas. Large, bulky 40 to 50 year old exchangers may be at the end oftheir useful life. Many times a facility is built up around thesefailing units and replacing them with a similarly sized unit wouldentail major demolition. Vertical exchangers can be wheeled through adoorway and they can be piped up with the existing unit in place,causing minimal downtime. Sometimes the existing unit is encapsulatedand left in place.

Attempts have been made to solve some of these problems, such as in U.S.Pat. No. 6,857,467 issued to Lach, the contents of which are hereinincorporated by reference. The Lach patent claims to disclose a “heatexchange system . . . used for heating a first fluid with a second fluid[using] . . . a flooded heat exchanger . . . capable of being flooded ina determined proportion [and] . . . includes a second fluid circuitcontrol valve . . . for controlling the flow rate of the second fluid .. . whereby the proportion of the heat exchanger which is flooded . . .can be selectively calibrated. The heat exchange system also includes afirst fluid pre-heating device . . . for partly pre-heating the firstfluid before it is heated by the second fluid, whereby the first fluidtemperature at the first fluid circuit downstream end will bestabilized.” Although the Lach patent attempts to improve thetemperature stability of a first fluid leaving the heat exchanger, theLach patent fails to provide a mechanism for stabilizing and reducingthe output temperature of the cooled fluid.

Semi-instantaneous water heaters attempt to stabilize the outputtemperature of water heaters by having small mixing tanks in which waterdelivered from the heat exchanger is blended with water in the vessel.U.S. Pat. No. 4,278,069 issued to Clark discloses an example of asemi-instantaneous water heater, the contents of which are hereinincorporated by reference. While it is possible to obtain temperaturecontrol of the warmed fluid in semi-instantaneous water heaters, theoutput temperature of the cooled fluid is uncontrolled.

Although designs by Lach and Clark have attempted to solve some of theproblems associated with heat exchangers, all of these problems have yetto be fully addressed. Objects of the present invention includeproviding a fluid heater with a low installation cost, providing a moreefficient heat transfer from steam, providing a heat exchanger thatrequires less physical space, providing a heat exchanger that does notrequire a condensate pump, a vacuum breaker, or a pressure regulatingvalve station, controlling the temperature of the liquid leaving theheat exchanger within ±3° F., and decreasing the temperature of thesteam condensate leaving the heat exchanger.

SUMMARY OF THE INVENTION

A dual fluid heat exchange system is presented that provides a stableoutput temperature for a heated fluid while also minimizing the outputtemperature of a cooled fluid. The heated and cooled fluids are broughtinto thermal contact with each other in a tank. The output temperatureof the warmed fluid is maintained at a stable temperature by are-circulation loop that connects directly to a mid portion of the tanksuch that the re-circulated fluid flow primarily warms only are-circulation section of the tank. The other, lower flow rate, sectionof the tank may be positioned so that it has a cooler temperature andthus serves to increase the efficiency of the heat exchanger byextracting extra heat energy out of the cooled fluid before it leavesthe tank. Alternatively, the low flow rate section of the tank may bewarmer than the re-circulated section, and thus allow the re-circulatedsection to be cooler than the final output temperature of the warmedfluid.

The cooled fluid may be condensed in a controlled manner from a vaporform to a liquid within the tank in order to release energy to heat thewarmed fluid. A control valve downstream of the tank may be used toadjust the condensate flow rate out of the tank in order to control therelative proportion of vapor to condensate.

The two warmed fluid sections of the tank may be structured so thatthere is no barrier between them, or there may be a separator to reduceunintended mixing between the sections. The structure of the tank forbringing the warmed and cooled fluids into thermal contact may include aplurality of vertical thermally-conductive pipes and a plurality ofhorizontal plates.

The foregoing summary does not limit the invention, which is defined bythe attached claims. Similarly, neither the Title nor the Abstract is tobe taken as limiting in any way the scope of the disclosed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Each of the drawing figures now described shows an exemplary embodimentof the present invention.

FIG. 1 is a schematic view of a heat exchange system with are-circulation circuit.

FIG. 2 is a schematic view of another heat exchange system with are-circulation loop.

FIG. 3 is a schematic view of a heat exchange system with are-circulation loop that includes a storage tank.

FIG. 4 is a schematic view of a heat exchange system with are-circulation loop that draws fluid from the midsection of a tank andtransfers the fluid to an inlet line.

FIG. 5 is a schematic view of a heat exchange system with are-circulation loop and a reverse flow mechanism in a condensate outputline.

FIG. 6 is a schematic view of a heat exchange system where fluid leavesthe system from a re-circulation circuit.

FIG. 7 is a graphic representation of a high flow fluid temperaturegradient within a heat exchanger tank having a re-circulation loop.

FIG. 8 is a graphic representation of a low flow fluid temperaturegradient within a heat exchanger tank having a re-circulation loop.

FIG. 9 is a cross-sectional view of a heat exchange tank having aplurality of vapor-vapor condensate containing pipes extending between avapor inlet and a vapor condensate outlet.

FIG. 10 is another cross-sectional view of a heat exchange tank having aplurality of vapor-vapor condensate containing pipes extending between avapor inlet and a vapor condensate outlet.

FIG. 11 is a cross-sectional view of a heat exchange tank having aplurality of vapor-vapor condensate containing pipes and a dividerbetween a pre-warming section and a re-circulation section.

FIG. 12 is another cross-sectional view of a heat exchange tank having aplurality of vapor-vapor condensate containing pipes and a dividerbetween a pre-warming section and a re-circulation section.

FIG. 13 is a cross-sectional view of a heat exchange tank having aplurality of horizontally oriented vapor-vapor condensate containingplates.

FIG. 14 is another cross-sectional view of a heat exchange tank having aplurality of horizontally oriented vapor-vapor condensate containingplates.

FIG. 15 is a cross-sectional view of a heat exchange tank having aplurality of densely packed horizontally oriented vapor-vapor condensateplates.

FIG. 16 is another cross-sectional view of a heat exchange tank having aplurality of densely packed horizontally oriented vapor-vapor condensateplates.

FIG. 17 is a cross-sectional view of a heat exchanger tank having abrazed plate construction where two fluids flow on alternating levels inopposite directions.

FIG. 18 is another cross-sectional view of a heat exchange tank having abrazed plate construction where two fluids flow on alternating levels inopposite directions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may be used with any type of heat exchanger and isparticularly suited for use with domestic hot water systems, ammoniabased refrigeration systems, heating water/glycol building heat systems,oil or heat transfer fluid systems, wash stations, and emergencyshowers. However, for descriptive purposes, the present invention willbe described in use with a heat exchanger heating water with hot steam.

FIG. 1 shows a circuit diagram of a heat exchange system with a heatexchange tank 10. A water circuit connecting to the heat exchange tankhas a water input line 15 for inputting cool water into the tank at acool water input 20 on the tank, and a water output line 25 withdrawingheated water from a hot water outlet 30 on the tank. A stabilizationcircuit with a re-circulation line 35 and a re-circulation pump 40diverts a portion of the heated water leaving the tank back into thetank at a re-circulated water inlet 45 to stabilize the temperature ofthe water leaving the tank. The re-circulation pump may be a variablespeed pump so that the flow rate through the recirculation line may beadjusted based on the temperature of the water in the tank and/or theflow rate of water into and out of the system.

A vapor circuit includes a steam input line 50 that provides hot steamto the heat exchange tank 10 at a steam inlet 55 on the tank. A driptrap 60 may be connected to the steam input line to remove condensationfrom the steam line. Within the tank, the steam is placed in thermalcommunication with the water from the water input line. Since the steamis at a higher temperature than the water, heat is transferred from thesteam to the water causing the steam to condense into a steam condensatewhile the water is warmed. The interface between the steam and the watermay be structured in a variety of ways to facilitate heat transfer fromthe steam to the water. In one embodiment of the invention, the steam isconfined to a plurality of vertically oriented tubes extending theheight of the tank while the water to be warmed substantially surroundseach of the tubes. In another embodiment of the invention, the steam isconfined to a steam conduit close to the exterior of the tank such thatthe conduit is only partially surrounded by water and only a portion ofthe conduit is structured to facilitate thermal communication betweenthe steam and the water. In yet another embodiment of the invention, thesteam in the tank is confined to a conduit having a plurality of bafflesstructured to increase the interior surface area of the conduit andthereby facilitate heat transfer from the steam to the water. The steamand water may progress through the tank in a co-current direction, orthe steam and water may travel in a counter co-current direction suchthat the steam input is located near the water output and the waterinput is located near the condensate output.

The steam/water interface is preferably made from thermally conductivematerials such as copper (380 W/mk thermal conductivity), aluminum (200W/mk), silver, (429 W/mk), type 304, 316, or 302 stainless steel (16.2W/mk), type 410 stainless steel (24.9 W/mk), or CoolPoly® E5101Thermally Conductive Polyphenylene Sulfide (20 W/mk).

A condensate line 65 withdraws steam condensate via a condensate outlet70 in the tank. A condensed steam outlet 75 may be in the condensateline to release condensate in the event of an over pressurization. Acontrol valve 80 in the condensate line is structured to restrict theflow of condensate out of the heat exchanger tank. By limiting the flowof condensate, the steam conduit within the tank may be fully orpartially flooded with steam condensate. As a result of the condensatehaving a greater density than the steam, the condensate will sink to thelower portions of the tank thereby forming a steam/condensate partitionwithin the tank. The condensation of steam in the steam section releasesa greater amount of heat energy into the water than the cooling of thesteam condensate allowing the water near the steam to be significantlyheated relative to the water near the steam condensate. By decreasingthe temperature of condensate leaving the heat exchanger tank, theefficiency of the heat exchanger is increased. Downstream of the controlvalve 80 is a condensate trap 85 adapted to prevent the flow a steam inthe event of a control valve failure. A bleed valve may be positionednear the condensate trap to release steam in the event of anunintentional vaporization.

FIG. 2 illustrates a heat exchanger tank 10 where the re-circulatedwater input 45 is located between the hot water outlet 30 and thecondensate outlet 70 such that a pre-warming section 90 within the tankis formed between the cool water inlet 20 and the re-circulated waterinlet 45. In the water flow downstream of the pre-warming section, are-circulation section 95 is located in the heat exchange tank betweenthe re-circulation input and the hot water outlet. Within there-circulation section, the water is exposed to hot condensate andcondensing steam such that the average temperature of the water withinthe re-circulation section to be greater than in the pre-warming sectionof the tank.

In the re-circulation section of the heat exchanger tank, the water hasan average flow rate that is higher than in the pre-warming sectionbecause the water in the re-circulation section is moved by both there-circulation pump and the means that moves the water through the coolwater input line, such as a water tower. The higher flow rate of there-circulation section facilitates heat transfer from the steam byacting to reduce the likelihood that water near the steam conduit issubstantially warmer than the rest of the re-circulation section.Additionally, the higher flow rate increases mixing within there-circulation section and thereby assists in stabilizing thetemperature of the water leaving the hot water output of the waterheater tank. In one embodiment, the pre-warming and re-circulationsections are substantially equal in size. In other embodiments, onesection may be larger than the other section. In an exemplaryembodiment, the pre-warming section is between 25% and 200% the size ofthe re-circulation section.

In order to optimize heat transfer from the steam and condensate to thewater, it is desirable to structure the tank so that the steamcondensate leaves the tank at a cool temperature. Preferably, thetemperature of the water in the pre-warming section should be as cold aspossible while the water in the re-circulation section should be nearthe desired hot output temperature. Thus, the temperature gradientbetween the two sections should be maximized. In order to create anoptimal temperature gradient, the flow of water from the pre-warmingsection to the re-circulation section is preferably limited to only aflow rate similar to the flow rate out of the heat exchange system. Theheat exchanger tank may be structured to limit the unintentional flowrate. In one embodiment, the re-circulated water input is structured sothat the re-circulated water enters the re-circulation section with avelocity that moves it away from the pre-warming section. In anotherembodiment, an aperture between the pre-warming section and there-circulation section functions to limit mixing between the twosections. In yet another embodiment, the two sections have baffles thatincrease intra-sectional mixing, but decrease unintentional mixingbetween the two sections. For example, the baffles may be oriented suchthat the water re-circulation section flows in a continuous upwardspiral.

The embodiment shown in FIG. 3 includes a storage tank 100 in there-circulation loop designed to increase the total volume of water inthe loop. By storing heat energy in the storage tank, the system is ableto efficiently store energy during low usage conditions. During highusage conditions, the water in the storage tank may be directly mixedinto the water input line 15 to warm the water before it enters the heatexchanger tank, or the water from the storage tank may be fed into there-circulated water inlet of the heat exchanger tank. If the water inthe storage tank is fed directly into the water input line 15, adiverter valve 105 in the line may be used to force a portion of thecool water to be fed into the storage tank through a bypass line 110.

FIG. 4 illustrates a heat exchanger tank where the water drawn by there-circulation pump 40 is drawn from a re-circulation outlet 115 on theheat exchange tank 10 that is separate from the hot water outlet 30 onthe tank. In the illustrated example, the water in the re-circulationline flows to the water input line 15, however in another embodiment,the re-circulated water is fed back into the tank via a separatere-circulated water inlet. In the system shown in FIG. 4, are-circulation section 95 in the tank is formed between the cool waterinput and the re-circulation output. Located downstream of there-circulation section is a post-warming section 120 where the water isfurther heated before it leaves the system through the water output line25. Since additional heating is done before the water leaves the system,the temperature of the water in the re-circulation loop can be somewhatless than the desired temperature of the water at the output.

FIG. 5 illustrates an example of a heat exchange system having a reverseflow mechanism 125 in the condensate line 65 and a lock valve 130 in thesteam input line 50 for decreasing or stopping the flow of steam intothe heat exchange tank. If the proportion of condensate to steam withinthe heat exchanger tank is below a desired amount, the lock valve canisolate the heat exchange tank from new steam. As the steam in the tankcools and condenses, a relative vacuum will form within the steamportion of the heat exchange tank. As a result of the relative vacuum,the condensate will be drawn back into the heat exchange tank. If thecondensate is warmer than the water in the heat exchange tank,additional heat energy will be transferred from the condensate to thesteam and the efficiency of the heat exchange system will be furtherincreased. The system may also include a condensate evacuationcircuit(not shown) extending between the condensate line 65 and thesteam input line 50 for draining condensed steam from the steam inputline.

FIG. 6 illustrates an example of a heat exchange system where the entirehot water output of the heat exchange tank 10 travels through there-circulation pump 40. The heated water output from the system is drawndirectly from the re-circulation line 35 while the water input line 15also feeds directly into the re-circulation line. In this design, there-circulation section occupies substantially the entire heat exchangetank. Due to the amount of mixing between the re-circulated water andwater from the input line, the system configuration of FIG. 6 providesheated water with an exceptionally consistent temperature. Theconfiguration of FIG. 6 is also able to maintain a consistent watertemperature during bursts of extremely high water usage.

FIG. 7 shows a representative graph of the water temperature within theheat exchanger tank 10 of FIG. 2 relative to the water's location withinthe tank during a high usage (100 gallons per minute) condition. Whenthe water enters the tank it has a relatively low temperature 135 thatincreases as the water absorbs heat from the steam condensate as itmoves through the pre-warming section. The low temperature of the waterallows the condensate temperature to also be low which increases theefficiency of the heat transfer within the tank. At or near thepre-warming/re-circulation section divide 140, the temperature of thewater jumps as it is mixed with hot re-circulated water. Once the waterenters the re-circulation section, its flow rate increases and itstemperature increase as it absorbs heat energy from the condensing steamand/or the steam condensate.

FIG. 8 shows a representative graph of the water temperature within theheat exchanger tank 10 of FIG. 2 relative to the water's location withinthe tank during a low usage (2 gallons per minute) condition. When waterenters the tank it has a relatively low temperature 135 that increasesas the water absorbs heat from the steam condensate moving through thepre-warming section. Since the water has a greater exposure time in thepre-warming section relative to the high flow conditions, the amount ofheat energy absorbed from the steam condensate is greater. As the waterenters the re-circulation section of the heat exchanger, the temperatureagain jumps as it mixes with the re-circulated water. In there-circulation section, the rate at which the temperature of the waterincreases relative to its position is less than in the high flow ratesdue to less of a temperature gradient between the steam/steam condensateand the water.

FIGS. 9 and 10 show perspective cross-sectional views of the interior ofa heat exchanger tank 10 with a steam inlet 55, a condensate outlet 70,and a re-circulated water inlet 45. The tank connects to a water inputline 15, a water output line 25, a re-circulation line 35, a steam inputline 50, and a condensate line 65. Within the tank are a plurality offloodable steam pipes 145, or conduits, extending between the steaminlet and the condensate outlet. The illustrated pipes have smalldiameters relative to the tank so that the pipes have a high surfacearea to interior volume ratio that facilitates the transfer of heatenergy from the steam or steam condensate. Additionally, the pipes arespaced apart so that the water may easily flow within the tank in orderto minimize the occurrence of local water hot spots. In the illustratedexample the pipes are substantially straight, however in otherembodiments the pipes may be curved so as to increase the path lengththat the steam/steam condensate must travel from the steam inlet to thecondensate outlet. In the illustrated example, the pipes aresubstantially uniform in their diameter, however in other examples thediameter of the pipes may be larger closer to the condensate outlet suchthat the condensate has a longer period of time to be cooled by thewater from the water input line.

In the example illustrated in FIGS. 9 and 10, the water flowing throughthe water input line 15 has a temperature of 65° F. and a flow rate of 1GPM. The water leaving the heat exchanger tank through the water outputline 25 has a temperature of 140° F. and a flow rate of 3 GPM. The waterentering the heat exchanger tank through the re-circulation line 35 hasa flow rate of 2 GPM and the temperature of the water close to there-circulated water inlet has a temperature of 120° F. The temperatureof the steam entering the tank through the steam input line is 300° F.,and the condensate leaving the tank has an average temperature of 100°F. The in the illustrated example, the average density of the waterwithin the re-circulation section is 0.98803 g/mL while the averagedensity of the water within the pre-warming section is 0.99821 g/mL suchthat the water in the re-circulation section floats on the water in thepre-warming section.

FIGS. 11 and 12 show perspective cross-sectional views of a heatexchange tank 10 with a section divider 150 between the pre-warming andre-circulation sections. The divider is structured to minimize the flowof heat energy from the re-circulation section to the pre-warmingsection while not hindering the replenishment of the re-circulationsection when hot water is drawn out of the system. In the illustratedexample a disk serves as the section divider, however other types ofdividers may be utilized. For example, a wire mesh may be placed betweenthe sections. The re-circulated water inlet 45 is substantiallyseparated from the cool water inlet, the hot water inlet, the steaminlet, and the condensate outlet so that the pre-warming section and there-circulation sections within the tank are similar in volume. Theseparation of the re-circulated water inlet also assists in preventingunnecessary heating of the condensate.

In the example illustrated in FIGS. 11 and 12, the water flowing throughthe water input line 15 has a temperature of 10° C. and a flow rate of1.9 liters per second. The water leaving the heat exchanger tank throughthe water output line 25 has a temperature of 75° C. and a flow rate of4.1 L/s. The water entering the heat exchanger tank from there-circulation line 35 has a flow rate of 2.2 L/s and the temperature ofthe water close to the re-circulated water inlet has a temperature of72° C. The temperature of the steam entering the tank through the steaminput line is 250° C., and the condensate leaving the tank has anaverage temperature of 60° C.

FIGS. 13-16 illustrate cross-sectional views of heat exchange tankswhere the steam within the tank travels through a plurality ofhorizontal plates 155 before leaving through the condensate outlet 65.The plates are structured so that the incoming and outgoing watercirculates around the plates. The illustrated plates are horizontallyoriented such that they do not substantially inhibit the horizontalcirculation of the water while limiting the vertical water circulation.Limiting the vertical flow of water helps to maintain the pre-warmingsection of the tank at a lower temperature than the re-circulationsection which improves the efficiency of the heat transfer. In theillustrated example, the water flowing through the water input line 15has a temperature of 300 K and a flow rate of 2.0 liters per second. Thewater leaving the heat exchanger tank through the water output line 25has a temperature of 350 K and a flow rate of 6.0 L/s. The waterentering the heat exchanger tank from the re-circulation line 35 has aflow rate of 4.0 L/s and the temperature of the water close to there-circulated water inlet has a temperature of 345 K. The temperature ofthe steam entering the tank through the steam input line is 525 K, andthe condensate leaving the tank has an average temperature of 360 K.

FIGS. 17 and 18 illustrate an example of a brazed plate style heatexchanger where the steam and water flow in opposite directions onalternating levels 160 formed by the brazed plates. The brazed platesmay have a non-smooth surface 165 adapted to increase the turbulence ofthe water and steam/steam condensate to thereby improve the efficiencyof the heat transfer.

Although the heat exchanger system has been described in regards toheating water, the heat exchanger can also be used for radiant heatingsystems. In those instances, the fluid being warmed may include amountsof other substances such as glycol, sodium titrate, NOBURST® HydronicSystem Cleaner, E-3 Defoaming Agent, and INHIBITOR BOOST. Otherchemicals may also be added to the fluid to inhibit corrosion, preventfreezing, increase the boiling point of the fluid, inhibit the growth ofmold and bacteria, and allow for improved leak detection (for example,dyes that fluoresce under ultraviolet light). Based on the fluid beingwarmed, the heat exchanger tank may be structured accordingly. Forexample, the pre-warming and re-circulation sections of the heatexchanger may be lined with a protective film if the warmed fluid issomewhat corrosive.

While the principles of the invention have been shown and described inconnection with specific embodiments, it is to be understood that suchembodiments are by way of example and are not limiting. Consequently,variations and modifications commensurate with the above teachings, andwith the skill and knowledge of the relevant art, are within the scopeof the present invention. The embodiments described herein are intendedto illustrate best modes known of practicing the invention and to enableothers skilled in the art to utilize the invention in such, or otherembodiments and with various modifications required by the particularapplication(s) or use(s) of the present invention. It is intended thatthe appended claims be construed to include alternative embodiments tothe extent permitted by the prior art.

1. A stabilized heat exchange system for regulating the temperatures ofboth a first and second fluid leaving the heat exchange system, thesystem comprising: a heat exchanger wherein the first and second fluidsare in adjacent, thermally-conductive contact facilitating heat transferfrom the second fluid to the first fluid to warm the first fluid from acool temperature when entering the heat exchanger to a warm temperaturewhen exiting the heat exchanger; the second fluid condensing from a gasto a liquid within the heat exchanger, wherein the relative proportionsof the gas to the liquid within the heat exchanger are regulated by asecond fluid control valve; the second fluid control valve in adownstream flow of the second fluid from heat exchanger for controllingthe flow rate of the second fluid through the heat exchanger, whereinthe proportion of the heat exchanger that is flooded with the liquid canbe selectively calibrated; and a stabilization circuit directing aproportion of warm temperature first fluid exiting the heat exchanger tobe re-circulated back into the heat exchanger where the warm temperaturefirst fluid is admixed with first fluid at an intermediate temperaturebetween the cool and warm temperatures.
 2. The stabilized heat exchangesystem of claim 1, wherein the second fluid exits the heat exchanger ata condensate temperature that is less the intermediate temperature andgreater than the cool temperature.
 3. The stabilized heat exchangesystem of claim 1, wherein the first fluid with the cool temperatureentering the heat exchanger has a first average flow rate, the firstfluid with the warm temperature exiting the heat exchanger has a secondaverage flow rate, and the second average flow rate is substantiallygreater than the first average flow rate.
 4. A heat exchange system forheating a liquid with a steam, wherein a temperature stabilizer acts todecrease temperature variability of the liquid exiting a tank by recirculating a portion of the liquid back into the tank, the systemcomprising: the tank including a liquid conduit including an inlet, aoutlet and a middle portion in between, the liquid conduit structured toallow the liquid to flow from the liquid inlet through the liquid middleportion to the liquid outlet, a steam conduit including an inlet, aoutlet and a middle portion in between, the steam conduit structured toallow the steam to flow from the steam inlet through the steam middleportion to the steam outlet, and a flooded heat exchanger where themiddle portions of the liquid and steam conduits extend and are inadjacent, thermally-conductive contact for facilitating heat transferfrom the steam to the liquid, the flooded heat exchanger being capableof being flooded with a steam condensate in a determined proportionwithin the steam conduit middle portion; a steam control valvecontrolling a flow rate of steam condensate through the steam conduit toselectively control the proportion of the heat exchanger that is floodedwith steam condensate; and a stabilization circuit having are-circulation inlet linked to the liquid conduit outlet; and are-circulation outlet, distant from both the liquid conduit inlet andoutlet, linked to middle portion of the liquid conduit, for allowing adetermined proportion of heated liquid exiting the tank to bere-circulated from the re-circulation inlet to the re-circulation outletwhere the heated liquid is mixed with the liquid in the tank at asection of the tank distant from the liquid conduit inlet, the liquidconduit outlet, the steam conduit inlet, and the steam conduit outlet,whereby the liquid temperature at the liquid conduit outlet will bestabilized, and the re-circulated outlet is distant from the steamconduit outlet to reduce unnecessarily heating of the steam condensateconduit outlet.
 5. The heat exchange system of claim 4, wherein theliquid has a first flow rate through the liquid conduit inlet, a secondflow rate through the liquid conduit outlet, and a third flow ratethrough the re-circulation outlet, wherein the sum of the first andthird flow rates is equal to second flow rate.
 6. A container forwarming a fluid to a consistent temperature by condensing a vapor, andfor pre-warming the fluid with a vapor condensate, the containercomprising: a pre-warming section including a cool fluid input forreceiving the fluid in a cool state; a re-circulation section includinga hot fluid output and a recirculated fluid input, the re-circulationsection structured to receive a portion of the fluid from the hot fluidoutput back into the re-circulation section through the recirculatedfluid input, whereby the recirculated portion of fluid mixes with fluidhaving an intermediate temperature greater than the temperature of thefluid in the cool state; and a condensate tube extending through boththe pre-warming section and the re-circulation section of the container,the tube structured to facilitate heat transfer from both the vapor andthe vapor condensate to the fluid in both the pre-warming section andthe re-circulation section.
 7. The container of claim 6 wherein thefluid has a first average flow rate through the pre-warming section, asecond average flow rate through the re-circulation section, and thesecond average flow rate is greater than the first average flow rate. 8.The container of claim 6 wherein the pre-warming section is structuredto contain a first volume of the fluid, the re-circulation section isstructured to contain a second volume of the fluid, and the first volumeis between 25% and 200% the size of the second volume.
 9. The containerof claim 6 wherein the fluid in the re-circulation section has a lowerdensity than the fluid in the pre-warming section, and the pre-warmingsection is located below the re-circulation section such that the fluidin the recirculation section will float above the fluid pre-warmingsection.
 10. A heat exchange system, including the container of claim 6,for heating the fluid by means of condensing the vapor and cooling thevapor condensate, the system comprising: a fluid circuit including anupstream end, a downstream end and an intermediate portion therebetween,the fluid circuit being destined to allow the fluid to flow from thefluid circuit upstream end to the fluid circuit downstream end; avapor/vapor condensate circuit comprising an upstream end, a downstreamend, and an intermediate portion therebetween that includes thecondensate tube, the vapor/vapor condensate circuit being destined toallow the vapor/vapor condensate to flow from the vapor/vapor condensatecircuit upstream end to the vapor/vapor condensate circuit downstreamend; the container of claim 6, wherein the intermediate portions of thefluid and vapor/vapor condensate circuits extend and are in adjacent,thermally-conductive contact for allowing heat transfer from thevapor/vapor condensate to the fluid, the intermediate portion of thefluid circuit extending from the cool fluid input to the hot fluidoutput, the container being capable of being flooded in a determinedproportion within the vapor/vapor condensate circuit intermediateportion; a vapor/vapor condensate circuit control valve on vapor/vaporcondensate circuit downstream of the container, for controlling the flowrate of the vapor/vapor condensate through the vapor/vapor condensatecircuit, wherein the proportion of the container which is flooded withinthe vapor/vapor condensate circuit intermediate portion can beselectively calibrated; and a stabilization circuit re-circulating aproportion of heated fluid exiting the container from the hot fluidoutput to the re-circulated fluid input where the heated fluid isadmixed with fluid flowing from the cool fluid input to the hot fluidoutput whereby the fluid temperature at the hot fluid output will bestabilized.
 11. The heat exchange system of claim 10, wherein thecontainer is a vertical flooded heat exchanger unit comprising aplurality of condensate tubes forming the vapor/vapor condensate circuitintermediate portion, with the fluid circuit intermediate portionextending around the plurality of condensate tubes on a shell side ofthe heat exchanger.
 12. The heat exchange system of claim 11, whereinthe stabilization circuit comprises a variable flow rate pump forpumping the fluid from the hot fluid output to the re-circulated fluidinput.
 13. The heat exchange system of claim 10 wherein the fluid has afirst average flow rate through the pre-warming section, a secondaverage flow rate through the re-circulation section, and the secondaverage flow rate is greater than the first average flow rate.
 14. Theheat exchange system of claim 10 wherein the pre-warming section isstructured to contain a first volume of the fluid, the re-circulationsection is structured to contain a second volume of the fluid, and thefirst volume is between 25% and 200% the size of the second volume. 15.The heat exchange system of claim 10 wherein the fluid in there-circulation section has a lower density than the fluid in thepre-warming section, and the pre-warming section is located below there-circulation section such that the fluid in the re-circulation sectionwill float above the fluid pre-warming section.
 16. The heat exchangesystem of claim 10, further comprising a steam trap located on thevapor/vapor condensate circuit downstream of the control valve, thesteam trap having a steam lock release option for allowing vapor to beevacuated from the vapor/vapor condensate circuit; and a bleed valve onthe vapor/vapor condensate circuit between the control valve and thesteam trap, for evacuating vapor.
 17. The heat exchange system of claim10, further comprising a vapor condensate evacuation circuit extendingbetween the vapor/vapor condensate circuit upstream and downstream ends,for allowing vapor condensate to be evacuated from the vapor/vaporcondensate circuit upstream end to the vapor/vapor condensate circuitdownstream end.
 18. A thermal energy transfer system for transferringheat energy to a first fluid from a second fluid, the system comprising:a first fluid circuit including an inlet, a outlet and an a middleportion in between, the first fluid circuit structured to allow thefirst fluid to flow from the first fluid circuit inlet to the firstfluid circuit outlet; a second fluid circuit including an inlet, aoutlet and a middle portion in between, the second fluid circuitstructured to allow the second fluid to flow from the second fluidcircuit inlet to the second fluid circuit outlet; a heat exchangerwherein the middle portions of the first fluid and second fluid circuitsextend and are in adjacent, thermally-conductive contact forfacilitating heat transfer from the second fluid to the first fluid, theheat exchanger floodable in a determined proportion within the secondfluid circuit middle portion; a second fluid circuit control valve onthe second fluid circuit downstream of the heat exchanger, forcontrolling a second fluid flow rate of the second fluid through thesecond fluid circuit, where the proportion of the heat exchanger that isflooded within the second fluid circuit middle portion can beselectively calibrated; and a stabilization circuit having are-circulation inlet linked to the first fluid circuit between the heatexchanger and the first fluid circuit outlet, and a re-circulationoutlet linked to the heat exchanger, for allowing a determinedproportion of heated first fluid exiting the heat exchanger to bere-circulated from the re-circulation inlet to the re-circulation outletwhere the heated first fluid is admixed with partially warmed firstfluid flowing within the heat exchanger whereby the first fluidtemperature at the first fluid circuit outlet will be stabilized. 19.The system of claim 18, wherein the heat exchanger further includes aplurality of thermally conductive plate sections for facilitating heattransfer from the second fluid to the first fluid.
 20. The system ofclaim 18, wherein the stabilization circuit further includes a variableflow rate pump for pumping the first fluid from the re-circulation inletto the re-circulation outlet.
 21. The system of claim 18, wherein thesecond fluid circuit further includes a vapor trap located downstream ofthe second fluid control valve.
 22. The system of claim 18, where thestabilization circuit further includes: a pump for pumping the firstfluid from the re-circulation inlet to the re-circulation outlet; astorage tank both fluidly connecting between the first fluid circuitinlet and the heat exchanger, and the re-circulation outlet and the heatexchanger, the storage tank allowing a determined proportion of heatedfirst fluid exiting the heat exchanger to be re-circulated from there-circulation inlet to the re-circulation outlet where the heated firstfluid is admixed with first fluid flowing from the first fluid circuitinlet, whereby the first fluid within the tank is preheated during smalldemand periods, and alternatively cooled during large demand periods.23. A system of claim 18 further comprising a drainage line for removingcondensed second fluid from between the second fluid circuit inlet atthe heat exchanger unit, the drainage line including a drainage inletlocated between the second fluid circuit inlet and the heat exchanger,and a drainage outlet located between the heat exchanger and the secondfluid circuit outlet.
 24. The system of claim 18, wherein the firstfluid within the flooded heat exchanger unit flows in a co-currentdirection to the second fluid within the flooded heat exchanger.
 25. Thesystem of claim 18 wherein the first fluid within the flooded heatexchanger unit flows in a co-current direction to the second fluidwithin the flooded heat exchanger.
 26. The system of claim 18 furthercomprising a second fluid shutoff valve between the second fluid circuitinlet and the flooded heat exchanger unit for selectively stopping theflow of second fluid into the flooded heat exchanger unit and forming alow pressure region within the flooded heat exchanger; and the secondfluid circuit control further includes a reverse flow mechanism forallowing fluid second fluid to be drawn back into the flooded heatexchanger unit towards the low pressure region.
 27. A method of heatinga first fluid with a second fluid within a heat exchange system, themethod comprising the steps of: circulating the first fluid through afirst fluid circuit including an upstream end, a downstream end, and aflooded section of a heat exchanger therebetween; circulating the secondfluid through a second fluid circuit including an upstream end, adownstream end, and a condensing section of the heat exchangertherebetween, wherein within the heat exchanger the first and secondfluid circuits are in adjacent, thermally-conductive contact wherebyheat from the second fluid is transferred to the first fluid; condensingthe second fluid within the flooded heat exchanger to form a condensateoccupying from 0% to 100% of the condensing section within the heatexchanger; selectively adjusting the heat exchange capacity of the heatexchanger unit by adjusting the flow rate of the second fluid throughthe heat exchanger to vary the volume of the condensate in thecondensing section; pre-heating the first fluid, within a pre-heatingregion flooded section, with heat from the condensate; and stabilizingthe temperature of the first fluid leaving the heat exchanger byre-circulating a portion of the first fluid in the downstream end offirst fluid circuit end back into the heat exchanger where there-circulated portion mixes with first fluid leaving the pre-heatingregion.